Often, it is desirable to know the location of a wireless user. In fact, it is sometimes necessary. For example, for an enhanced 911 (E-9-1-1) wireless service, the location of a mobile station (e.g., a cellular phone) may be provided to a Public Safety Answering Point (PSAP) each time a 911 call is made from the mobile station. Further, a network operator/service provider may support various applications that use location based services. Such services provide the location of mobile stations. The term “applications” refers to the particular uses that are made of location information. Often times, applications are implemented with computer software that is either executed by a processor within a mobile station or by a processor located within a component of a wireless infrastructure network that is in communication with the mobile station. Applications that use this information may include, for example, location-sensitive billing, asset tracking, asset monitoring and recovery, fleet and resource management, personal-location services, and so on. Some specific examples of applications for personal-location services include (1) providing a local map to a mobile station based on its location, (2) providing a recommendation for a facility (e.g., a hotel or a restaurant) based on the mobile station's location, and (3) providing directions to the recommended facility from the mobile station's current location.
There are many different types of technologies that may be employed in calculating the location of mobile stations in wireless networks with various levels of success and accuracy. Examples of location technologies include Satellite Positioning Systems (SPS's) (including the United States' Global Positioning System (GPS), the Russian GLObal NAvigation Satellite System (GLONASS), the European Galileo System, the Chinese Compass/Beidou System, etc.), Advanced Forward Link Trilateration (AFLT), timing advance (TA), and terrestrial-based enhanced observed time difference (E-OTD) position fixing. Various positioning technologies use devices such as satellites and/or wireless communication network devices (e.g., base stations, WiFi stations, etc.) to determine mobile device positions.
Different techniques/technologies have different abilities to locate mobile devices. The variation in location abilities depends on several factors such as number of location devices, range of the location devices, environment of the mobile device, etc.